During the exploitation of shale gas, it is necessary to conduct reservoir reconstruction for the purpose of economic recovery. Workers in North America and China now adopt the method of combining drilling and completion of horizontal well with massive hydraulic fracturing, which needs enormous amount of water and sand. The interaction of these fluids and reservoir rocks lays the foundation for the success of reservoir reconstruction, whereas the initial water saturation of reservoirs and the understanding of causes of this state are premises of the method. With studies of the marine shale gas reservoirs in southern China, it is found that gas-enriched reservoir often has ultra-low water saturation, which is caused by hydrocarbon generation, consumption and evaporation, etc. Ultra-low water saturation improves adsorption capacity of shale, extends the movable pore throat radius, and increases the gas phase permeability. However, it also accelerates the water-base rates of adsorption and permeation, deteriorates water and hydrocarbon phase trapping problems, and brings more potential damages to aqueous phase trapping of shale gas. Under this circumstance, more attention needs to be paid to the negative effect of ultra-low water saturation and its work damage during the evaluation, reconstruction, and development of shale gas reservoirs.
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